Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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SPECIFIC~TION
AIR INT~RCEPTIV~ sT~ucTunE IN A
REF~ACTO~Y ST~UCTUnE
~FIELD OF ~nT~
This invention relates to an air interceptive structure
in a refractory structure, such as a nozzle device for
steelmaking, and in particular, a sliding nozzle device used
for the treatment of pure steel.
(BACKGROUND OF THE INVENTION~
~ ccording to one process fQr oasting molten ~teel
refined in a converter3 eleotric furnace, etc., the molten
steel is recelved in a ladle, ancl is continuou31y cast
thr-ough a tunclish.
In order to make a oast product of pure steel, it is
very important to prevent steel oxidation as oauqed by
contact with open air during casting. A oasting proce~s in
which steel is isolated from open air is called an air-
isolated oasting prooess.
One air-isolated oasting prooess is carried out by
feeding molten steel through a tube called a shroud, or
through a submerged nozzle, to prevent it from exposure to
open air while it flows down.
If a sliding nozzle device is used to control the
downward flow of molten steel, however, air is drawn in
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through the joints of bricks in the device, or through the
joints between the shroud or the submerged nozzle and the
sliding nozzle device. No satisfactory isolation from air
can, therefore, be achieved by the air-isolated casting
process employing only the shroud or the submerged nozzle.
There have been various solutions proposed regarding the
problem oE the air drawn in through the joints as is
hereinabove pointed out. For example, Japanese Patent Laid-
Open Application No. 62-50070 proposes the use of a sliding
nozzle device having a wholly closed structure defini~g a
clos2d atmosphere into which an inert gas, such as argon, ls
blown, and Japanese ~atent Laid-Open ~pplioation No. Gl-3653
proposes the evacuatlon of such a closed chamber.
~ large-scale apparatus is, however, required for
carrying out any of the methods which have hitherto been
proposed, and none of the methGds can produce a satisfactory
result of isolation, despite the apparatus employed. The
joints of the shroud or the submerged nozzle are, among other
things, so constructed as to make it practically impossible
to define a closed environment to prevent the molten steel to
be cast from exposure to air. The joints of the refractories
forming the shroud or the submerged nozzle are formed by
mortar or sealing material, but as the downward flow of the
molten steel creates a considerably high negative pressure in
the bore of the sliding nozzle device through which the
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molten steel is caused to flow down, no satisfactory sealing
effect can be expected from t.he mortar or sealing material
alone.
It is a first object of this invention to provide a
structure which ensures the isolatlon of molten steel from
air in a refractory structure, such as a sliding nozzle
device having a molten steel outlet.
It is a second object of this invention to provide a
device whîch is simple in construction, particularly in the
construction of suction piping and other related equipment,
and yet ensures the i~olation of molten qteel f`rom air in a
refractory 9 tructure.
~DISCLOSU~E OF T~IE INVENTION)
This invention relates to a structure for interoeptlng
air in a refractory ~tructure comprising refractory materials
having a nozzle bore for downward flow of molten steelg in
which a groove for venting air is formed around the nozzle
bore, and communicated with a passage leading to an outside
air venting device.
It also provides a simple structure for venting air
which comprises one or more passages formed in a member
composed of refractory materials and having a nozzle bore,
and leading to an outside air venting device, the member
having grooves formed around the nozzle bore and communicated
with the passages leading to the outside device.
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The grooves for venting air which are formed in the
refraotory materials surrounding the nozzle bore work
effectively creating a negative pressure in the joints of the
refractory materials. Thus, there is no invasion of air into
the nozzle bore through the joints of the refractory
materials.
When a sliding nozzle is employed, the nozzle bore
defined by plate bricks can be filled with molten steel, if
the nozzle bore is plaoed at a negative pressure whlch ls
higher than that which is created by the control of its flow
rate, and which is in the level of say, 10 to 70 cm ~Ig.
As a oonsequence, it is possible to eliminate any lack
of uniformity in the rlow o~ molten steel injected into a
mold, or tundi3h, and thereby prevent any entrainment of
inclusions that might otherwise occur.
~ ccording to this invention, therefore, the use of
appropriately shaped bricks enables a considerably high level
of reliability in the air-isolated casting of molten steel at
low cost, and the connecting holes to whioh the exhaust
grooves formed in the joint surfaces are connected provide a
simple device.
~BRIEF DESCRIPTION OF DRAWINGS)
Fig. 1 shows a sliding nozzle device comprising three
plates including a slidable middle plate, and embodying this
invention;
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Figs. 2(a), 2(b) and 2(c) are top plan views of air
venting grooves according to this invention a~ taken along
the lines ~ B-B, and A'-~' or B'-B', respectively, of Fig.
1 ;
Fig. 3 is a top plan view of another form of grooves
rormed in a slidable middle plate; and
Figs. 4 and 5 show still other emt70diments.
~DESCRIPTION OF THE PREFERRED EMBODIMENT~
The invention will now be described with reference to a
sliding nozzle devioe embodying it.
Fig. 1 shows a sliding noææle device whloh is located
under an upper nozzle 1 provided at the bottom of a tundish
8, and comprises a stationary upper plate 2, a slldable
middle plate 3 and a stationary lower plate 11, and under
which a lower nozzle 5 and a submerged nozzle 6 are mounted.
The joint between each two adjoining refractory
structures as described above is provided with at least one
U-shaped groove 9 extending about a nozzle bore 7 formed
substantially in the center thereof.
Figs. 2(a), 2(b) and 2(c~ are top plan views of the
plates 2, 3 and 4, respectively, as taken along the lines ~-
A, B-B, and ~ ' or B'-B', respectively, of Fig. 1, and
showing the grooves 9 formed therein. The U-shaped grooves
are so positioned that the grooves of the stationary upper
plate 2 and the slidable middle plate 3 are communicated with
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each other, while those of the slidable middle plate 3 and
the stationary lower plate 4 are also communicated with eaoh
other, when molten steel is caused to flow.
Fig. 3 shows a circular Kroove 9 as an example of
modiflcation.
Each groove 9 is associated with a piece of briclc having
an exhaust hole 10 and can be evacuated by a vacuum pump
mounted outside, though not shown, so that the air tending to
invade through the joint between the upper nozzle 1 and the
stationary upper plate 2, between the stationary upper plate
2 and the slidable middle plate 3, between the slldablc
middle plate 3 and the stationary lower plate ll, between the
stationary lower plate ll and the lower nozzle 5, or between
the lower nozzle 5 ancl the submerged nozzle 6 may be drawn
out through the exhaust hole 10 which is partially connected
to the groove 9 by the vacuum pump before it enters the
nozzle bore 7.
Figs. 4 and 5 show still more embodiments. Fig. 4 is a
top plan view oE a slidable middle plate 3 constituting a
modified form of the plate structure shown in Fig. 1 or 3,
and having a bore connecting grooves 9 with an exhaust hole
10. Fig. 5 is a sectional view of an assembly of the
slidable middle plate 3 shown in Fig. 4, and stationary upper
and lower plates 2 and 4.
~ s shown in these figures, the grooves g2 and 93 formed
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in the stationary upper and lower plates, respectively, and
e~tending about the nozzle bore 7 are communicated with the
hole 11 extending through the sl.idable middle plate 3, and
with the passage 10 f`ormed in the stationary upper plate 2
and leading to an outside air venting device, when the
slidable middle plate 3 has been caused to slide to open the
nozzle bore 7.
This structure makss it sufficient to provide only one
passage of the nature shown at 10 in ~ig. 3, and thereby
enables the simplification of the related piping, while a
plurality of holes 10 are required of` the struature shown in
Fig. 1.
~INDUST~IAL FE~SIBIL,ITY~
This invention is applicable not only to a sliding
nozzle devioe comprising three plates as hereinabove
described by way of example, but also to a device comprising
two plates including a slidable lower plate, or combination
of a plate (or plates) and a shroud or a submerged nozzle.
Moreover, it is not limited to a sliding nozzle device, but
is also applicable to any other nozzle, or pipe, or device
for handling molten metal which need be isolated from the
open air.
